Prevention of infiltration of gas bubbles into slurry pump parts

ABSTRACT

In a slurry pump of liquid-diaphragm type having a diaphragm chamber containing a portion of slurry being pumped and a lighter diaphragm liquid, gas bubbles existing in large concentration in the slurry are prevented from infiltrating into the diaphragm chamber by the injection of a seal liquid without bubbles into the slurry in the chamber to cause a flow of liquid counter to the direction of infiltration of the gas bubbles. For this purpose, a seal-liquid-injection pipe is installed in the slurry in the chamber and supplied by a pump with the seal liquid from a reservoir through a check valve.

United States Patent 1 Kazama et a1.

[54] PREVENTION OF INFILTRATION OF GAS BUBBLES INTO SLURRY PUMP PARTS[75] Inventors: Toshio Kazama; Kazunori Sek, both of Nagaoka, Japan [73]Assignee: Tamagawa Kikai Kinzoku Kabushiki Kaisha, Tokyo-to, Japan [22]Filed: Apr. 19, 1971 [21] Appl.-No.: 134,945

[30] Foreign Application Priority Data Sept. 21, 1970 Japan 45/82838[56] References Cited UNITED STATES PATENTS 3,241,496 lmai et al 417/98Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. GluckAttorneyRobert E. Burns [5 7] ABSTRACT In a slurry pump ofliquid-diaphragm type having a diaphragm chamber containing a portion ofslurry being pumped and a lighter diaphragm liquid, gas bubbles existingin large concentration in the slurry are prevented from infiltratinginto the diaphragm chamber by the injection of a seal liquid withoutbubbles into the slurry in the chamber to cause a flow of liquid counterto the direction of infiltration of the gas bubbles. For this purpose, aseal-liquid-injection pipe is installed in the slurry in the chamber andsupplied by a pump with the seal liquid from a reservoir through a checkvalve.

19 Claims, 1 Drawing Figure PREVENTION OF INFILTRATION OF GAS BUBBLESINTO SLURRY PUMP PARTS BACKGROUND OF THE INVENTION This inventionrelates generally to slurry pumps of the liquid-diaphragm type and moreparticularly to a new method and apparatus for preventing gas bubbles ina slurry being pumped from infiltrating into the diaphragm and pistonparts of a slurry pump.

Slurry pumps with which this invention is concerned are of the classdescribed in Japanese Pat. publication No. 12131/1960, U.S. Pat. No.3,241,496, patented Mar. 22, 1966, British Pat. No. 1,187,912, patentedAug. 12, 1970, and South African Pat. No. 68/0753, patented May 30,1969.

Among the various fluid substances referred to as slurries, there arethose, such as caustic bauxite slurries and limestone slurriescontaining viscosity-reducing agents, which contain a large number ofgas (air) bubbles. When a liquid of this nature is handled by means of aslurry pump of the liquid-diaphragm type, a portion of the bubblescontained in the liquid separate out and accumulate in theliquid-diaphragm chamber and thereby give rise to the followinginconveniences and difficulties.

l. Frequent extraction of the accumulated gas (degasification ordeaeration) becomes necessary,

whereby the pump operation requires additional lahour.

2. The bubbles carry solid particles into the diaphragm liquid (oil),whereby the liquid becomes contaminated, and the particles tend to causewear of the piston parts.

3. The gas (air) causes a reduction in the pump delivery, while cloggingdue to settling of the particles easily occurs.

Accordingly, it is necessary to prevent the bubbles from passing fromthe pump valve box through the connecting pipe and infiltrating into theliquid-diaphragm chamber and to cause the bubbles to move rapidly fromthe suction valve through the discharge valve and be promptly dischargedtherefrom without stagnating or slowing down within the pump.

SUMMARY OF THE INVENTION It is an object of this invention to fulfil theabove stated requirement in slurry pumps of the liquiddiaphragm type.More specifically, an object of the invention is to provide a method andapparatus for preventing gas bubbles in a liquid containing a largequantity of bubbles and being pumped by a liquiddiaphragm slurry pumpfrom infiltrating into the diaphragm chamber.

According to the present invention, briefly summarised, there areprovided a method and apparatus for preventing infiltration of gasbubbles as described above, wherein a seal liquid without gas bubbles isinjected into the slurry in the liquid-diaphragm chamber thereby tocreate a liquid flow counter to the direction of the infiltration of gasbubbles into the diaphragm chamber.

The nature, principle, and utility of the invention will be more clearlyapparent from the following detailed description with respect to apreferred embodiment of the invention when read in conjunction with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, the single FIGURE is adiagrammatic side elevation, in vertical section, showing the essentialparts of a slurry pump of liquid-diaphragm type and indicating anexample of practice of the invention.

DETAILED DESCRIPTION The principal components of the slurry pumpillustrated in the drawing are a plunger pump 1, a valve box 4, and anoil-diaphragm chamber 11 connected be tween the plunger pump and thevalve box.

The plunger pump 1 has a cylinder 3 filled with oil and connected by wayof an oil connecting pipe 12 to the upper part of the chamber 11 and aplunger 2 driven by means not shown and operating as a piston within thecylinder 3. The valve box 4 has a slurry suction pipe 9 and a slurrydischarge pipe 10 and is provided internally with spacedapart valveseats 5 and 6 for cooperatively operating with ball valves 7 and 8,respectively, acting on the downstream sides of their valve seats tofunction as check valves for preventing reversal of slurry flow. Amiddle chamber 4a is formed between the two ball valves and communicatesby way of a slurry connecting pipe 13 to the bottom of the oildiaphragmchamber 11.

The chamber 11 is provided thereabove with an oil reservoir tank 14communicating through a shut-off valve 15 to the upper part of thechamber 11. The upper part of this oil-diaphragm chamber 11 contains oil22 communicating integrally with the oil in the pipe 12 and cylinder 3,while the lower part of the chamber 11 contains slurry 20 communicatingintegrally with the slurry in the pipe 13 and chamber 4a, an interface21 being formed naturally between the oil 22 and slurry 20 because ofthe difference in the specific gravities thereof.

The liquid-diaphragm slurry pump of the above described organization isknown, and the organization and operation thereof are disclosed ingreater detail in the aforementioned references.

In accordance with this invention there is provided a method andapparatus for preventing infiltration of gas bubbles into theoil-diaphragm chamber 1 1. One example of this apparatus, as illustratedin the drawing, comprises a reservoir tank 18 for storing the motherliquor of the slurry not containing any bubbles and constituting a sealliquid, a liquid injection pipe 19 disposed in the lower part of theoil-diaphragm chamber 11, a booster'pump l7, driven by motive powermeans (not shown), for pumping the seal liquid from the tank 18 into theinjection pipe 19, a check valve 16 disposed between the pump 17 and theinjection pipe 19 for preventing reversal flow of the seal liquid, andnecessary piping and pipeline accessories (not shown).

This apparatus is operated, during the pumping operation of the slurrypump, to inject at a low flowrate the seal liquid without bubblesinto-the slurry 20 in the lower part of the oil-diaphragm chamber 11thereby to force back gas bubbles traveling through the slurry pipe 13and tending to enter into the chamber 11. The bubbles are, thusinhibited from traveling toward the chamber 11 and caused to bedischarged through the slurry discharge pipe 10.

During the suction stroke of the plunger pump 1, the check valve 16permits the seal liquid to flow freely into the chamber 1 1. During thedischarge stroke of the plunger pump 1, the check valve 16 operates toprevent reverse flow or return of the injected liquid or entrance ofslurry into the injection pipe 19, whereby the slurry is sent in thenormal manner toward the slurry pipe 13. Since the seal liquid is thusinjected a little at a time into the chamber 11 during the suctionstroke of the plunger pump 1, a net flow of liquid is created throughthe slurry pipe 13 from the oil-diaphragm chamber 11 toward the valvebox 4, whereby the quantity of gas bubbles tending to enter the chamber11 becomes progressively less.

Thus, the present invention provide a method and apparatus which, whenapplied to a slurry pump of liquiddiaphragm type, afford a saving inoperational labour, eliminate the possibility of excessive wear of theslurry pump parts due to contamination of the diaphragm liquid, andenable the pump to operate stably with a steady delivery without thepossibility of settling of particles to cause clogging even when theslurry pump is operated to pump slurry containing a large quantity ofgas bubbles.

It should be understood, of course, that the foregoing disclosurerelates to only a specific embodiment of the invention and that it isintended to cover all changes and modifications of the example of theinvention herein chosen for the purposes of the disclosure, which do notconstitute departures from the spirit and scope of the invention. Forexample, instead of the booster pump 17 used in the above describedexample, a driving pressure generating source of another kind can beused. In addition, the apparatus according to the invention may includecontrol means 23 to control automatically the flowrate of the sealliquor supplied into the chamber 11 and means 24 to detect theconcentration of gas bubbles in the slurry 20 and to generatecorresponding signals in response to which the control means can operateto control the flowrate accordingly.

We claim: 7

1. For use in a slurry pump of the type having a liquid-diaphragmchamber containing in operation a slurry and a diaphragm liquid incontact therewith defining an interface therebetween, a method ofpreventing gas bubbles entrained in said slurry from infiltrating intosaid diaphragm liquid comprising injecting a seal liquid without gasbubbles into the slurry in said chamber to create a liquid flow counterto the direction of said infiltration of gas bubbles.

2. A method as claimed in claim 1 in which said seal liquid is themother liquor without gas bubbles of the slurry being pumped.

3. In a slurry pump of the type having a liquiddiaphragm chambercontaining in operation a slurry and a diaphragm liquid in contacttherewith defining an interface therebetween, an apparatus forpreventing gas bubbles entrained in said slurry from in filtrating thediaphragm liquid, said apparatus comprising a reservoir containing aseal liquid without gas bubbles, liquid-injection means for injectingsaid seal liquid into the slurry in the liquid-diaphragm chamber, meansdefining a flow path from said reservoir to said liquidinjection means,liquid-transfer means for transferring seal liquid from said reservoirthrough said flow path to said liquid-injection means, and a check valvedisposed between the liquid-transfer means and liquid-injection meansfor preventing reverse flow in said flow path.

4. Apparatus as claimed in claim 3 in which said seal liquid is themother liquor without gas bubbles of the slurry being pumped.

5. Apparatus as claimed in claim 3 in which there are provided detectingmeans for detecting the concentration of gas bubbles in the slurry inthe liquid-diaphragm chamber to generate corresponding signals andcontrol means operating in response to said signals to control theflowrate of the seal liquid through the flow path.

6. In combination, a slurry pump having a liquiddiaphragm chamber forcontaining in operation a slurry and a diaphragm liquid thereabovedefining an interface therebetween, an apparatus for preventing gas in agaseous phase entrained in said slurry from infiltrating into saiddiaphragm liquid, said apparatus comprising means to apply underpressure a seal liquid free of entrained gases to said slurry in saidliquid-diaphragm chamber in a counter flow path directed away from saidinterface and in an area effective to substantially prevent infiltrationof said gas into said interface.

7. Apparatus as claimed in claim 6, in which said means for applyingsaid seal liquid comprises a reservoir containing said seal liquid,liquid-injection means for injecting said seal liquid into said slurryin said liquid-diaphragm chamber, liquid-transfer means to supply saidseal liquid from said reservoir to said liquidinjection means.

8. Apparatus as claimed in claim 7, including a check valve disposedbetween said liquid-transfer means and said liquid-injection means toprevent reverse flow toward said liquid-transfer means.

9. Apparatus as claimed in claim 7, including sensing means detectingthe concentration of said gas entrained in said slurry, control meansresponsive to said sensing means to control the flow rate of said sealliquid to said liquid-injection means.

10. Apparatus as claimed in claim 6, in which said seal liquid comprisesthe component liquid of said slurry.

11. For use in conjunction with a slurry pump having a liquid-diaphragmchamber for containing in operation slurry and a diaphragm liquidthereabove defining an interface therebetween, an apparatus forpreventing gas in a gaseous phase entrained in said slurry frominfiltrating into said diaphragm liquid, said apparatus comprising meansto apply under pressure a seal liquid free of entrained gases to saidslurry in said liquiddiaphragm chamber in a counter flow path directedaway from said interface and in an area effective to substantiallyprevent infiltration of said gas into said interface.

12. The apparatus as claimed in claim 11, in which said seal liquidcomprises the component liquid of said slurry.

13. The apparatus as claimed in claim 11, in-which said means forapplying said seal liquid comprises a reservoir containing said sealliquid, liquid-injection means for injecting said seal liquid into saidslurry in said liquid-diaphragm chamber, and liquid-transfer means tosupply said seal liquid from said reservoir to said liquid-injectionmeans.

14. The apparatus as claimed in claim 13, including a check valvedisposed between said liquid-transfer means and said liquid-injectionmeans to prevent reverse flow toward said liquid-transfer means.

15. The apparatus as claimed in claim 13, including sensing meansdetecting the concentration of said gas entrained in said slurry,control means responsive to said sensing means to control the flow rateof said seal liquid to said liquid-injection means.

16. A method of preventing infiltration of gas bubbles into a liquiddefining an interface with a mixture of a liquid with insoluble mattercomprising, applying a seal liquid free of bubbles under pressure tosaid mixture in the vicinity of said interface as a counter flowdirected to flow away from said interface and in an area effective tosubstantially prevent infiltration of said gas into said interface.

17. A method as claimed in claim 16, in which said seal liquid comprisesthe component liquid of said liquid mixture.

18. For use in a slurry pump having a liquiddiaphragm chamber forcontaining in operation a slurry and a diaphragm liquid thereabovedefining an interface therebetween, a method of preventing gas bubblesentrained in said slurry from infiltrating into said diaphragm liquidcomprising, applying under pressure a seal liquid free of bubbles tosaid slurry in said liquiddiaphragm chamber in the vicinity of saidinterface and directed to flow away from said interface and in an areaeffective to substantially prevent infiltration of said gas bubbles intosaid interface.

19. A method as claimed in claim 18, in which said seal liquid comprisesthe component liquid of said slurry.

1. For use in a slurry pump of the type having a liquiddiaphragm chambercontaining in operation a slurry and a diaphragm liquid in contacttherewith defining an interface therebetween, a method of preventing gasbubbles entrained in said slurry from infiltrating into said diaphragmliquid comprising injecting a seal liquid without gas bubbles into theslurry in said chamber to create a liquid flow counter to the directionof said infiltration of gas bubbles.
 2. A method as claimed in claim 1in which said seal liquid is the mother liquor without gas bubbles ofthe slurry being pumped.
 3. In a slurry pump of the type having aliquid-diaphragm chamber containing in operation a slurry and adiaphragm liquid in contact therewith defining an interfacetherebetween, an apparatus for preventing gas bubbles entrained in saidslurry from in filtrating the diaphragm liquid, said apparatuscomprising a reservoir containing a seal liquid without gas bubbles,liquid-injection means for injecting said seal liquid into the slurry inthe liquid-diaphragm chamber, means defining a flow path from saidreservoir to said liquid-injection means, liquid-transfer means fortransferring seal liquid from said reservoir through said flow path tosaid liquid-injection means, and a check valve disposed between theliquid-transfer means and liquid-injection means for preventing reverseflow in said flow path.
 4. Apparatus as claimed in claim 3 in which saidseal liquid is the mother liquor without gas bubbles of the slurry beingpumped.
 5. Apparatus as claimed in claim 3 in which there are provideddetecting means for detecting the concentration of gas bubbles in theslurry in the liquid-diaphragm chamber to generate corresponding signalsand control means operating in response to said signals to control theflowrate of the seal liquid through the flow path.
 6. In combination, aslurry pump having a liquid-diaphragm chamber for containing inoperation a slurry and a diaphragm liquid thereabove defining aninterface therebetween, an apparatus for preventing gas in a gaseousphase entrained in said slurry from infiltrating into said diaphragmliquid, said apparatus comprising means to apply under pressure a sealliquid free of entrained gases to said slurry in said liquid-diaphragmchamber in a counter flow path directed away from said interface and inan area effective to substantially prevent infiltration of said gas intosaid interface.
 7. Apparatus as claimed in claim 6, in which said meansfor applying said seal liquid compRises a reservoir containing said sealliquid, liquid-injection means for injecting said seal liquid into saidslurry in said liquid-diaphragm chamber, liquid-transfer means to supplysaid seal liquid from said reservoir to said liquid-injection means. 8.Apparatus as claimed in claim 7, including a check valve disposedbetween said liquid-transfer means and said liquid-injection means toprevent reverse flow toward said liquid-transfer means.
 9. Apparatus asclaimed in claim 7, including sensing means detecting the concentrationof said gas entrained in said slurry, control means responsive to saidsensing means to control the flow rate of said seal liquid to saidliquid-injection means.
 10. Apparatus as claimed in claim 6, in whichsaid seal liquid comprises the component liquid of said slurry.
 11. Foruse in conjunction with a slurry pump having a liquid-diaphragm chamberfor containing in operation slurry and a diaphragm liquid thereabovedefining an interface therebetween, an apparatus for preventing gas in agaseous phase entrained in said slurry from infiltrating into saiddiaphragm liquid, said apparatus comprising means to apply underpressure a seal liquid free of entrained gases to said slurry in saidliquid-diaphragm chamber in a counter flow path directed away from saidinterface and in an area effective to substantially prevent infiltrationof said gas into said interface.
 12. The apparatus as claimed in claim11, in which said seal liquid comprises the component liquid of saidslurry.
 13. The apparatus as claimed in claim 11, in which said meansfor applying said seal liquid comprises a reservoir containing said sealliquid, liquid-injection means for injecting said seal liquid into saidslurry in said liquid-diaphragm chamber, and liquid-transfer means tosupply said seal liquid from said reservoir to said liquid-injectionmeans.
 14. The apparatus as claimed in claim 13, including a check valvedisposed between said liquid-transfer means and said liquid-injectionmeans to prevent reverse flow toward said liquid-transfer means.
 15. Theapparatus as claimed in claim 13, including sensing means detecting theconcentration of said gas entrained in said slurry, control meansresponsive to said sensing means to control the flow rate of said sealliquid to said liquid-injection means.
 16. A method of preventinginfiltration of gas bubbles into a liquid defining an interface with amixture of a liquid with insoluble matter comprising, applying a sealliquid free of bubbles under pressure to said mixture in the vicinity ofsaid interface as a counter flow directed to flow away from saidinterface and in an area effective to substantially prevent infiltrationof said gas into said interface.
 17. A method as claimed in claim 16, inwhich said seal liquid comprises the component liquid of said liquidmixture.
 18. For use in a slurry pump having a liquid-diaphragm chamberfor containing in operation a slurry and a diaphragm liquid thereabovedefining an interface therebetween, a method of preventing gas bubblesentrained in said slurry from infiltrating into said diaphragm liquidcomprising, applying under pressure a seal liquid free of bubbles tosaid slurry in said liquid-diaphragm chamber in the vicinity of saidinterface and directed to flow away from said interface and in an areaeffective to substantially prevent infiltration of said gas bubbles intosaid interface.
 19. A method as claimed in claim 18, in which said sealliquid comprises the component liquid of said slurry.